Imaging devices, such as scanners, copiers, facsimile machines, and multipurpose machines, are readily commercially available for converting tangible images (e.g., documents, photographs) or images of objects (e.g., the cover of a book) into electronic images. These imaging devices operate by generating light from a light source in the imaging device and reflecting this light off of the surface of the tangible image or object. The reflected light is collected on an array of photosensitive elements, which convert the reflected light into electronic signals representing the image.
Imaging devices may be provided with external media adaptors that can be used with the imaging devices for different types of media. For example, media adapters are available that employ back lighting (e.g., cold cathode fluorescent light bulbs) to back light semi-transparent images, such as overhead transparencies and film negatives.
Contact image sensor (CIS) imaging devices may employ light emitting diodes (LEDs) as the light source (or other suitable light source), and one or more rows of CIS sensors. CIS imaging devices tend to be thinner, lighter, more energy efficient, and less expensive than imaging devices employing optical reduction technology. However, CIS sensors use a gradient index lens array which have a limited depth of focus. Therefore, CIS imaging devices are not readily adaptable for use with conventional media adapters that use back lighting for imaging transparency media because of the thickness of the media or mounting location at some height above the surface of the scanner glass.